Marine vessel propulsion apparatus

ABSTRACT

A marine vessel propulsion apparatus includes a transom bracket, a steering shaft, an outboard motor, a steering mechanism, a first cylinder, and a second cylinder. The steering mechanism is arranged to turn the steering shaft and the outboard motor around the steering axis with respect to the transom bracket. The first cylinder is arranged to turn the outboard motor around the tilt axis between a first angle and a second angle larger than the first angle, and support the outboard motor between the first angle and the second angle. The second cylinder is arranged to turn the outboard motor around the tilt axis between the first angle and a third angle larger than the second angle, and support the outboard motor between the first angle and the third angle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a marine vessel propulsion apparatus.

2. Description of the Related Art

A conventional marine vessel propulsion apparatus is described in, forexample, Japanese Published Unexamined Patent Application No.2006-143066. This marine vessel propulsion apparatus includes two clampbrackets, a swivel bracket, a tilt shaft, an outboard motor, a steeringshaft, and a PTT mechanism (power trim & tilt mechanism).

Clamp brackets are attachable to the transom of the hull. Two clampbrackets are disposed at an interval in the right-left direction. Theswivel bracket is joined to the clamp brackets via the tilt shaftextending horizontally. The outboard motor is joined to the swivelbracket via the steering shaft extending in the up-down direction. Theswivel bracket and the outboard motor are turnable around a tilt axis(central axis of the tilt shaft) with respect to the clamp brackets. Theoutboard motor is turnable around a steering axis (central axis of thesteering shaft) with respect to the clamp brackets and the swivelbracket. The steering shaft turns with respect to the clamp bracketsaccording to turning of the outboard motor around the tilt axis.Therefore, the steering axis turns with respect to the clamp bracketsaccording to turning of the outboard motor around the tilt axis.

The PTT mechanism turns the outboard motor around the tilt axis withrespect to the clamp brackets by turning the swivel bracket around thetilt axis. The PTT mechanism supports the outboard motor in both of atrim range in which the tilting angle of the outboard motor is small anda tilt range in which the tilting angle of the outboard motor is largerthan in the trim range. The PTT mechanism turns the outboard motoraround the tilt axis in these ranges. The PTT mechanism includes a trimcylinder that supports the outboard motor in the trim range and turnsthe outboard motor in the trim range, and a tilt cylinder that supportsthe outboard motor in both of the trim range and the tilt range andturns the outboard motor in both ranges.

The trim cylinder and the tilt cylinder are disposed between the twoclamp brackets. At the rear of these cylinders, a portion of the swivelbracket is disposed, and ahead of these cylinders, the transom isdisposed. The cylinder main bodies of the cylinders are joined to theclamp brackets. The rod of the tilt cylinder is joined to the swivelbracket. In a state in which the outboard motor is positioned in thetrim range, the rod of the trim cylinder is in contact with the swivelbracket. When the tilting angle of the outboard motor exceeds the trimrange, the rod of the trim cylinder separates from the swivel bracket.Therefore, in the state in which the outboard motor is positioned in thetrim range, the outboard motor is supported by the trim cylinder and thetilt cylinder, and when the tilting angle of the outboard motor exceedsthe trim range, the outboard motor is supported only by the tiltcylinder.

Another conventional marine vessel propulsion apparatus is described in,for example, U.S. Pat. No. 6,146,220. This marine vessel propulsionapparatus includes a transom bracket, a steering shaft, an outboardmotor, a tilt shaft, and a tilt mechanism.

The transom bracket is attachable to the transom of the hull. Thesteering shaft is joined to the transom bracket. The steering shaftextends in the up-down direction. The outboard motor is joined to thesteering shaft via the tilt shaft extending horizontally. The outboardmotor is turnable around the tilt axis (central axis of the tilt shaft)with respect to the steering shaft. The steering shaft and the outboardmotor are turnable around the steering axis (central axis of thesteering shaft) with respect to the transom bracket. When the outboardmotor turns around the tilt axis, the steering shaft does not turn withrespect to the transom bracket. Therefore, the steering axis does notturn with respect to the transom bracket according to turning of theoutboard motor around the tilt axis.

The tilt mechanism turns the outboard motor around the tilt axis withrespect to the steering shaft. The tilt mechanism includes two tiltcylinders that support the outboard motor and turn the outboard motor.The two tilt cylinders are disposed in parallel to each other at aninterval. The steering shaft is disposed between two tilt cylinders. Theoutboard motor is disposed at the rear of the tilt cylinder, and thetransom bracket is disposed ahead of the tilt cylinder. The side of eachtilt cylinder is opened. The cylinder main body of each tilt cylinder isjoined to the steering shaft. The rods of the tilt cylinders are joinedto the outboard motor. The outboard motor is supported by the two tiltcylinders.

SUMMARY OF THE INVENTION

The inventors of preferred embodiments of the present inventiondescribed and claimed in the present application conducted an extensivestudy and research regarding a marine vessel propulsion apparatus, suchas the ones described above, and in doing so, discovered and firstrecognized new unique challenges and previously unrecognizedpossibilities for improvements as described in greater detail below.

In detail, the trim range is a range to be used mainly so as to adjustthe posture of the hull when the marine vessel runs forward, and thetilt range is a range to be used mainly when the marine vessel is mooredor runs in shallow water. The tilt range is a range in which the tiltingangle of the outboard motor is large, so that when the outboard motor ismoved from the trim range to the tilt range, the propeller may come outof the water. If the propeller comes out of the water when the marinevessel runs forward, the propulsive force to be transmitted to the hullis reduced. Therefore, if the outboard motor moves to the tilt rangewhen the marine vessel runs forward, the marine vessel may bedecelerated.

As described above, when the trim cylinder and the tilt cylinder areprovided, in the state in which the outboard motor is positioned in thetrim range, the outboard motor is supported by the trim cylinder and thetilt cylinder. Further, in the state in which the outboard motor ispositioned in the tilt range, the trim cylinder separates from theoutboard motor, and the outboard motor is supported only by the tiltcylinder. When the outboard motor moves from the trim range to the tiltrange, loads including the own weight of the outboard motor and theforward propulsive force that had been applied to the trim cylinder areapplied to the tilt cylinder, so that the loads to be applied to thetilt cylinder increase. Therefore, when the outboard motor moves fromthe trim range to the tilt range, the internal pressure of the tiltcylinder increases.

For example, in a case where the forward propulsive force is great, whenthe outboard motor moves from the trim range to the tilt range, theinternal pressure of the tilt cylinder increases. To the tilt cylinder,piping in which hydraulic oil circulates is connected, and to thispiping, a relief valve is attached. When the internal pressure of thetilt cylinder increases, the relief valve opens and the hydraulic oil isdischarged from the tilt cylinder. Accordingly, the projecting amount ofthe rod of the tilt cylinder is reduced, and the outboard motor returnsfrom the tilt range to the trim range. Therefore, the propeller can beprevented from coming out of the water when the marine vessel runsforward.

On the other hand, when the forward propulsive force is small or themarine vessel stops, even if the outboard motor moves from the trimrange to the tilt range, the internal pressure of the tilt cylinderrises only up to a pressure lower than in the case where the propulsiveforce is great, so that the relief valve does not open. Therefore, inthese cases, the outboard motor can be positioned in the tilt range.Further, when the outboard motor moves from the trim range to the tiltrange, the amount of hydraulic oil that had been supplied to the trimcylinder of the hydraulic oil fed from a hydraulic pump is supplied tothe tilt cylinder, so that the supply flow rate of hydraulic oil to thetilt cylinder increases. Therefore, the movement speed of the rod of thetilt cylinder increases, and the outboard motor turns around the tiltaxis at a speed higher than the movement speed in the trim range.Accordingly, the outboard motor can be quickly tilted up in the tiltrange.

In recent years, outboard motors have tended to be increased in sizeand/or output. If an outboard motor is large in size, the weight of theoutboard motor increases, so that the load to be applied to eachcylinder increases. The propulsive force of the outboard motor istransmitted to each cylinder, so that if the outboard motor has a highoutput, the load to be applied to each cylinder increases. Therefore, ifthe outboard motor is increased in size and/or output, the problem of anincrease in internal pressure of each cylinder occurs. For example, byincreasing the size of each cylinder main body, the internal pressureincrease can be reduced, and this problem can be solved. However, in themarine vessel propulsive apparatus described in Japanese PublishedUnexamined Patent Application No. 2006-143066, the PTT mechanism issurrounded by the clamp brackets, the swivel bracket, and the transom,so that if the trim cylinder and the tilt cylinder are increased insize, a new problem occurs in which these cylinders interfere with theclamp brackets, etc. Therefore, it is difficult to increase the size ofeach cylinder main body. In order to prevent the clamp brackets frominterfering with the cylinders, it is possible that the distance betweenthe right and left clamp brackets is increased by moving the clampbrackets outward. However, the attaching range of the clamp brackets tothe hull is regulated according to the standards, so that the problemcannot be solved even by this method.

On the other hand, in the marine vessel propulsion apparatus describedin U.S. Pat. No. 6,146,220, the outboard motor is supported by two tiltcylinders. The sides of the tilt cylinders are opened. Therefore, thecylinder main bodies can be increased in size. However, in this marinevessel propulsion apparatus, the trim cylinder is not provided, so thateven when the outboard motor moves from the trim range to the tilt rangewhile the forward propulsive force is great, the internal pressure ofthe tilt cylinder does not increase unlike the case where the trimcylinder is provided. Therefore, even if the above-described piping andrelief valve are provided, the outboard motor cannot be moved from thetilt range to the trim range. Therefore, the propeller may come out ofthe water when the marine vessel runs forward. Further, in the marinevessel propulsion apparatus described in U.S. Pat. No. 6,146,220, thetrim cylinder is not provided, so that the speed of turning of theoutboard motor around the tilt axis cannot be easily changed between thetrim range and the tilt range.

In the marine vessel propulsion apparatus described in U.S. Pat. No.6,146,220, in order to prevent the propeller from coming out of thewater during forward running of the marine vessel, it is possible that,for example, a sensor that detects the position of the outboard motor isprovided, and based on a detection value of this sensor, the supplyamount of the hydraulic oil to the tilt cylinder is controlled. However,in this case, the sensor and related devices are necessary, and thecontrol becomes complicated. Further, in the marine vessel propulsionapparatus described in U.S. Pat. No. 6,146,220, in order to change thespeed of turning of the outboard motor around the tilt axis between thetrim range and the tilt range, it is possible that the supply flow rateof the hydraulic oil to the tilt cylinder is changed. However, in thiscase, for example, the rotational speed of an electric motor that drivesthe hydraulic pump must be changed, and the control becomes complicated.

In order to overcome the previously unrecognized and unsolved challengesdescribed above, a preferred embodiment of the present inventionprovides a marine vessel propulsion apparatus including a transombracket, a steering shaft, an outboard motor, a steering mechanism, afirst cylinder, and a second cylinder. The transom bracket is arrangedto be attachable to the transom of the hull. The steering shaft isjoined to the transom bracket, and is arranged turnably around asteering axis extending in the up-down direction. The outboard motor isjoined to the steering shaft. The outboard motor is arranged turnablyaround a tilt axis extending along a plane perpendicular orsubstantially perpendicular to the steering axis. Further, the outboardmotor is arranged turnably around the steering axis together with thesteering shaft. The steering mechanism is joined to the transom bracketand the steering shaft. The steering mechanism is arranged to turn thesteering shaft and the outboard motor around the steering axis withrespect to the transom bracket. The first cylinder is joined to thesteering shaft and the outboardmotor. The first cylinder is arranged toturn the outboard motor around the tilt axis between a first angle and asecond angle larger than the first angle, and support the outboard motorbetween the first angle and the second angle. The second cylinder isjoined to the steering shaft and the outboard motor. The second cylinderis arranged to turn the outboard motor around the tilt axis between thefirst angle and a third angle larger than the second angle, and supportthe outboard motor between the first angle and the third angle.

With this arrangement of the present preferred embodiment of the presentinvention, the outboard motor is joined to the steering shaft. Theoutboard motor is turnable around the tilt axis extending along a planeperpendicular or substantially perpendicular to the steering axis withrespect to the steering shaft. The first cylinder and the secondcylinder are joined to the steering shaft and the outboard motor. Thefirst cylinder turns the outboard motor around the tilt axis between thefirst angle and the second angle larger than the first angle, andsupports the outboard motor between the first angle and the secondangle. The second cylinder turns the outboard motor around the tilt axisbetween the first angle and the third angle larger than the secondangle, and supports the outboard motor between the first angle and thethird angle.

Thus, the first cylinder supports the outboard motor between the firstangle and the second angle, and the second cylinder supports theoutboard motor between the first angle and the third angle.Specifically, the range (first range) in which the first cylindersupports the outboard motor is smaller than the range (first and secondranges) in which the second cylinder supports the outboard motor. In thefirst range (range between the first angle and the second angle), theoutboard motor is supported by the first cylinder and the secondcylinder, and in the second range (range excluding the first range inthe range between the first angle and the third angle), the outboardmotor is supported by the second cylinder. Therefore, in the state inwhich the forward propulsive force is great, when the outboard motormoves from the first range to the second range, the internal pressure ofthe second cylinder increases. Therefore, by discharging a hydraulicfluid from the second cylinder by using, for example, a relief valve,the outboard motor can be returned to the first range. Accordingly, theoutboard motor can be mechanically prevented from being positioned inthe second range during a high thrust. Further, the first cylinder andthe second cylinder are provided, so that the outboard motor can bemechanically quickly turned in the second range. Further, unlike theconventional marine vessel propulsion apparatus, the clamp brackets arenot disposed on the lateral sides of the cylinders, so that thecylinders can be increased in size. Accordingly, when the outboard motoris large in size or the outboard motor has a high output, the increasesin internal pressure of the cylinders can be minimized.

The steering shaft includes a tubular portion extending along thesteering axis, and at least a portion of the second cylinder may behoused inside the tubular portion. In this case, the increase in size ofthe marine vessel propulsion apparatus can be minimized.

The first cylinder and the second cylinder may be arranged to turnaround the steering axis together with the steering shaft.

The marine vessel propulsion apparatus may further include a pump thatsupplies hydraulic oil to the first cylinder and the second cylinder, anelectric motor that drives the pump, and a piping in which hydraulic oilcirculates, and the first cylinder, the second cylinder, the pump, theelectric motor, and the piping may be arranged to turn around thesteering axis together with the steering shaft.

It is possible that at least a portion of the pump is exposed, and atleast a portion of the electric motor is exposed. In this case, a userof the marine vessel propulsion apparatus can easily access the pump andthe electric motor. Therefore, the user can easily perform maintenanceoperations such as replacement of the hydraulic oil.

The marine vessel propulsion apparatus may further include a detachableprotective cover covering at least one of the pump and the electricmotor. In this case, at least one of the pump and the electric motor isprotected by the protective cover, so that at least one of the pump andthe electric motor can be prevented from being damaged. The protectivecover is detachable, so that a user of the marine vessel propulsionapparatus can expose the pump and the electric motor by detaching theprotective cover. Accordingly, the user can easily access the pump andthe electric motor. Therefore, the user can easily perform maintenanceoperations such as replacement of the hydraulic oil.

At least a portion of the piping may be exposed. In this case, thepiping can be easily accessed. Therefore, a user of the marine vesselpropulsion apparatus can easily perform maintenance operations such asreplacement of the piping, etc.

The outboard motor may include a tilt bracket joined to the steeringshaft. The tilt bracket may be turnable around the tilt axis withrespect to the steering shaft.

The second cylinder may be joined to the outboard motor via a firstturning shaft turnably around the first turning shaft with respect tothe outboard motor. Further, the second cylinder may be joined to thefirst cylinder via a second turning shaft turnably around the secondturning shaft with respect to the first cylinder. In detail, it is alsopossible that the rod of the second cylinder is joined to the outboardmotor via the first turning shaft, and the main body of the secondcylinder is joined to the first cylinder via the second turning shaft.It is also possible that the main body of the second cylinder is joinedto the outboard motor via the first turning shaft, and the rod of thesecond cylinder is joined to the first cylinder via the second turningshaft.

The first cylinder and the second cylinder may be disposed so as not tooverlap as viewed in a direction orthogonal or substantially orthogonalto the tilt axis.

It is also possible that the marine vessel propulsion apparatus includesa pair of the first cylinders disposed at an interval in a directionparallel or substantially parallel to the tilt axis, and the secondcylinder is disposed so that the second cylinder is positioned betweenthe pair of first cylinders as viewed in a direction orthogonal orsubstantially orthogonal to the tilt axis. In detail, it is possiblethat the second cylinder is disposed so that at least a portion of thesecond cylinder is positioned between the pair of first cylinders, andthe second cylinder is positioned between the pair of first cylinders asviewed in the direction orthogonal or substantially orthogonal to thetilt axis. It is also possible that the second cylinder is disposed sothat the second cylinder is not positioned between the pair of firstcylinders, and the second cylinder is positioned between the pair offirst cylinders as viewed in the direction orthogonal or substantiallyorthogonal to the tilt axis.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a first marine vessel propulsion apparatusaccording to a first preferred embodiment of the present invention.

FIG. 2 is a side view of the first marine vessel propulsion apparatusaccording to the first preferred embodiment of the present invention.

FIG. 3 is a plan view of the first marine vessel propulsion apparatusaccording to the first preferred embodiment of the present invention.

FIG. 4A is a perspective view of a portion of the first marine vesselpropulsion apparatus according to the first preferred embodiment of thepresent invention.

FIG. 4B is an exploded perspective view of a portion of the first marinevessel propulsion apparatus according to the first preferred embodimentof the present invention.

FIG. 4C is an exploded view of a portion of the first marine vesselpropulsion apparatus according to the first preferred embodiment of thepresent invention.

FIG. 5 is a back view of a tilt mechanism according to the firstpreferred embodiment of the present invention.

FIG. 6 is a partial sectional view of a portion of the first marinevessel propulsion apparatus including the tilt mechanism according tothe first preferred embodiment of the present invention.

FIG. 7 is a side view of a portion of the first marine vessel propulsionapparatus including the tilt mechanism according to the first preferredembodiment of the present invention.

FIG. 8 is a side view of a portion of the first marine vessel propulsionapparatus including the tilt mechanism according to the first preferredembodiment of the present invention.

FIG. 9 is a partial sectional view of a portion of the first marinevessel propulsion apparatus including a steering mechanism according tothe first preferred embodiment of the present invention.

FIG. 10 is a schematic plan view of a portion of the first marine vesselpropulsion apparatus including the steering mechanism according to thefirst preferred embodiment of the present invention.

FIG. 11 is a schematic plan view of a portion of the first marine vesselpropulsion apparatus including the steering mechanism according to thefirst preferred embodiment of the present invention.

FIG. 12 is a side view of a second marine vessel propulsion apparatusaccording to a second preferred embodiment of the present invention.

FIG. 13A is a perspective view of a portion of the second marine vesselpropulsion apparatus according to the second preferred embodiment of thepresent invention.

FIG. 13B is an exploded perspective view of a portion of the secondmarine vessel propulsion apparatus according to the second preferredembodiment of the present invention.

FIG. 13C is an exploded view of a portion of the second marine vesselpropulsion apparatus according to the second preferred embodiment of thepresent invention.

FIG. 14 is a partial sectional view of a portion of the second marinevessel propulsion apparatus according to the second preferred embodimentof the present invention.

FIG. 15 is a side view of the second marine vessel propulsion apparatusaccording to the second preferred embodiment of the present invention.

FIG. 16 is a plan view of the second marine vessel propulsion apparatusaccording to the second preferred embodiment of the present invention.

FIG. 17 is an exploded view of a portion of the second marine vesselpropulsion apparatus according to the second preferred embodiment of thepresent invention.

FIG. 18 is a partial sectional view of a portion of the second marinevessel propulsion apparatus including a steering mechanism according tothe second preferred embodiment of the present invention.

FIG. 19 is a schematic plan view of a portion of the second marinevessel propulsion apparatus including the steering mechanism accordingto the second preferred embodiment of the present invention.

FIG. 20 is a schematic plan view of a portion of the second marinevessel propulsion apparatus including the steering mechanism accordingto the second preferred embodiment of the present invention.

FIG. 21 is a back view of a portion of the second marine vesselpropulsion apparatus according to a third preferred embodiment of thepresent invention.

FIG. 22 is a plan view of a portion of the second marine vesselpropulsion apparatus according to the third preferred embodiment of thepresent invention.

FIG. 23 is a side view of a portion of the second marine vesselpropulsion apparatus according to the third preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a first marine vessel propulsion apparatus including anelectric motor fixed to the transom bracket and a second marine vesselpropulsion apparatus including an electric motor fixed to the steeringshaft will be described. The description given below is based on a statein which the outboard motor is in a reference posture. The referenceposture is a posture of the outboard motor when the tilting angle of theoutboard motor is zero and the steering angle of the outboard motor iszero. The tilting angle of the outboard motor is an angle of therotational axis (crank axis L1) of the crankshaft with respect to avertical plane. The tilting angle of the outboard motor 2 when the crankaxis L1 extends vertically is zero. The steering angle of the outboardmotor is an angle of the rotational axis (rotational axis L2) of thepropeller with respect to the center line of the hull. The steeringangle of the outboard motor when the rotational axis L2 of the propellerextends in the front-rear direction is zero. A direction toward one sideof the front-rear direction (forward direction) is a directionapproaching the transom, and the other direction of the front-reardirection (rearward direction) is a direction extending away from thetransom.

First Marine Vessel Propulsion Apparatus First Preferred Embodiment

FIG. 1 and FIG. 2 are side views of a first marine vessel propulsionapparatus 1 according to a first preferred embodiment of the presentinvention. FIG. 3 is a plan view of the first marine vessel propulsionapparatus 1 according to the first preferred embodiment of the presentinvention. FIG. 4A is a perspective view of a portion of the firstmarine vessel propulsion apparatus 1 according to the first preferredembodiment of the present invention. FIG. 4B is an exploded perspectiveview of a portion of the first marine vessel propulsion apparatus 1according to the first preferred embodiment of the present invention.FIG. 4C is an exploded view of a portion of the first marine vesselpropulsion apparatus 1 according to the first preferred embodiment ofthe present invention.

The first marine vessel propulsion apparatus 1 includes an outboardmotor 2. The outboard motor 2 is attached to a transom T1 provided onthe rear portion of the hull H1. The outboard motor 2 includes an engine3, an engine cover 4, and a casing 5. The engine 3 is housed inside theengine cover 4. The engine 3 includes a crankshaft 6. The crankshaft 6is rotatable around a crank axis L1. The crankshaft 6 is joined to adrive shaft (not shown). The drive shaft is joined to a propeller shaft(not shown). The drive shaft and the propeller shaft are housed in thecasing 5. The casing 5 includes an upper case 7 and a lower case 8disposed below the engine cover 4. The lower case 8 supports thepropeller 9 rotatably around a rotational axis L2. Rotation of thecrankshaft 6 is transmitted to the propeller 9 via the drive shaft andthe propeller shaft. The propeller 9 is rotatable in a forwardpropelling direction and a backward propelling direction opposite to theforward propelling direction. The propeller 9 is driven to rotate in theforward propelling direction and the backward propelling direction bythe engine 3.

The first marine vessel propulsion apparatus 1 includes a transombracket 10, a steering shaft 11, and a tilt shaft 12. The outboard motor2 includes a tilt bracket 13. The transom bracket 10 is attachable tothe transom T1. The transom bracket 10 includes a plate-shaped attachingportion 14 to be attached to the transom T1 and a tubular housingportion 15 disposed at the rear of the attaching portion 14. Thesteering shaft 11 is joined to the transom bracket 10. The tilt bracket13 is joined to the steering shaft 11 via the tilt shaft 12. Thesteering shaft 11 and the outboard motor 2 are turnable around asteering axis L3 extending in the up-down direction with respect to thetransom bracket 10. The outboard motor 2 is turnable around a tilt axisL4 extending in the horizontal direction with respect to the transombracket 10 and the steering shaft 11. The tilt axis L4 is a central axisof the tilt shaft 12.

As shown in FIG. 4B and FIG. 4C, the steering shaft 11 includes atubular portion 16, a joint portion 17, and an intermediate portion 18.The steering axis L3 is the central axis of the tubular portion 16. Thejoint portion 17 is joined to the upper end portion of the tubularportion 16 via the intermediate portion 18. The tubular portion 16, thejoint portion 17, and the intermediate portion 18 may be separatemembers as in this preferred embodiment, or may constitute an integralmember. Specifically, the steering shaft 11 may be a member including aplurality of divided bodies, or may be an integral member. The tiltbracket 13 is joined to the joint portion 17 via the tilt shaft 12. Thesteering shaft 11 is inserted in the housing portion 15 of the transombracket 10. The tubular portion 16 is housed in the housing portion 15.The housing portion 15 extends along the steering axis L3. The steeringshaft 11 is turnable around the steering axis L3 with respect to thetransom bracket 10.

The first marine vessel propulsion apparatus 1 includes a tilt mechanism19. The tilt mechanism 19 is joined to the steering shaft 11 and theoutboard motor 2. The tilt mechanism 19 turns the outboard motor 2around the tilt axis L4 with respect to the transom bracket 10 and thesteering shaft 11. The outboard motor 2 turns around the tilt axis L4with respect to the steering shaft 11, so that even if the tilting angleof the outboard motor 2 changes, the steering axis L3 does not move.Specifically, the steering axis L3 is an axis that does not move withrespect to the transom bracket 10. A direction in which the outboardmotor 2 tilts around the tilt axis L4 so that the upper end of the crankaxis L1 is positioned forward relative to the lower end of the crankaxis L1 is defined as a positive direction. A range in which the tiltingangle of the outboard motor 2 is small is a trim range, and a range inwhich the tilting angle of the outboard motor 2 is larger than the upperlimit of the trim range is a tilt range.

In FIG. 2, a state in which the tilting angle of the outboard motor 2 isthe lower limit (full trim-in angle) of the trim range is shown by thealternate long and short dashed lines, and a state in which the tiltingangle of the outboard motor 2 is the upper limit (full trim-out angle)of the trim range is shown by the alternate long and two short dashedlines. In FIG. 2, a state in which the tilting angle of the outboardmotor 2 is the upper limit (full tilt-up angle) of the tilt range isshown by the solid line. The full trim-in angle is an example of thefirst angle according to the first preferred embodiment of the presentinvention, and the full trim-out angle is an example of the second angleaccording to the first preferred embodiment of the present invention.The full tilt-up angle is an example of a third angle according to thefirst preferred embodiment of the present invention. The full trim-inangle is, for example, −5 degrees, and the full trim-out angle is, forexample, 15 degrees. The full tilt-up angle is, for example, 65 degrees.The tilt mechanism 19 can hold the outboard motor 2 at an arbitraryposition including the trim range and the tilt range. The trim range isa range to be used mainly when adjusting the posture of the hull H1 whenthe marine vessel is propelled forward, and the tilt range is a range tobe used mainly when the marine vessel is moored or runs in shallowwater.

The first marine vessel propulsion apparatus 1 includes a steeringmechanism 20. The steering mechanism 20 is joined to the transom bracket10 and the steering shaft 11. The steering mechanism 20 turns thesteering shaft 11 and the tilt shaft 12 around the steering axis L3 withrespect to the transom bracket 10. The outboard motor 2 and the tiltmechanism 19 turn around the steering axis L3 together with the steeringshaft 11 and the tilt shaft 12 according to turning of the steeringshaft 11. The tilt shaft 12 turns around the steering axis L3 togetherwith the outboard motor 2, so that the tilt axis L4 that is the centralaxis of the tilt shaft 12 turns around the steering axis L3 with respectto the transom bracket 10 according to turning of the outboard motor 2around the steering axis L3. The position of the outboard motor 2 whenthe steering angle of the outboard motor 2 is zero is defined as asteering origin. As shown in FIG. 3, the outboard motor 2 is turnable tothe right and left around the steering origin (the position shown by thesolid line). The steering mechanism 20 turns the outboard motor 2 aroundthe steering axis L3 between a maximum rightward steering position (theposition shown by the alternate long and short dashed lines) and amaximum leftward steering position (the position shown by the alternatelong and two short dashed lines). The steering mechanism 20 can hold theoutboard motor 2 at an arbitrary position between the maximum rightwardsteering position and the maximum leftward steering position.

FIG. 5 is a back view of the tilt mechanism 19 according to the firstpreferred embodiment of the present invention. Hereinafter, the tiltmechanism 19 will be described with reference to FIG. 4B, FIG. 4C, andFIG. 5.

The tilt mechanism 19 includes two trim cylinders 21, a tilt cylinder22, and a frame 23. Two trim cylinders 21 are disposed in parallel orsubstantially parallel to each other at an interval in the right-leftdirection, that is, a direction parallel or substantially parallel tothe tilt axis L4. Each trim cylinder 21 is disposed obliquely along thefront-rear direction so that the upper end of the trim cylinder 21 ispositioned rearward relative to the lower end of the trim cylinder 21.The tilt cylinder 22 extends in the up-down direction. The upper end ofthe tilt cylinder 22 (upper end portion of a tilt rod 27) is positionedhigher than the trim cylinders 21. The tilt cylinder 22 is disposed sothat the tilt cylinder 22 is positioned between the two trim cylinders21 as viewed in the front-rear direction, that is, a directionorthogonal or substantially orthogonal to the tilt axis L4.

Each trim cylinder 21 includes a cylinder main body 24 and a trim rod 25extending along the central axis of the trim cylinder 21. Each trim rod25 projects upward from the upper end of the cylinder main body 24. Eachcylinder main body 24 is fixed to the frame 23. On the other hand, thetilt cylinder 22 includes a cylinder main body 26 and a tilt rod 27extending along the central axis of the tilt cylinder 22. The tilt rod27 projects upward from the upper end of the cylinder main body 26. Thelower end portion of the cylinder main body 26 is joined to the frame 23via a lower pin 28 extending in the right-left direction. The tiltcylinder 22 is joined to the frame 23 and the trim cylinders 21 via thelower pin 28. The tilt cylinder 22 is turnable around the lower pin 28with respect to the frame 23 and the trim cylinders 21. The lower pin 28is an example of the second turning shaft according to the firstpreferred embodiment of the present invention.

The cylinders 21 and 22 preferably are, for example, hydrauliccylinders. The tilt mechanism 19 includes a pump 30 that supplieshydraulic oil, a tank 31 storing the hydraulic oil, an electric motor 32that drives the pump 30, and a plurality of pipes 33 connected to thepump 30 and the tank 31. The pump 30, the tank 31, the electric motor32, and the pipes 33 are held by the frame 23. The pump 30 and the tank31 are disposed at an interval in the right-left direction. The electricmotor 32 is disposed above the pump 30. The pump 30 and the electricmotor 32 are disposed above one trim cylinder 21, and the tank 31 isdisposed above the other trim cylinder 21. The tilt cylinder 22 isdisposed so that the tilt cylinder 22 is positioned between the pump 30and electric motor 32 and the tank 31 as viewed in the front-reardirection.

The frame 23 includes a seat portion 23 a disposed along a horizontalplane, a pair of projections 23 b projecting downward from the seatportion 23 a, and a support portion 23 c disposed along a horizontalplane above the seat portion 23 a. The pair of projections 23 b aredisposed at an interval in the right-left direction below the seatportion 23 a. The cylinder main body 24 of the trim cylinder 21 is fixedto the frame 23. In the first preferred embodiment, for example, thecylinder main body 24 of the trim cylinder 21 and the frame 23preferably are an integral casting. The cylinder main body 26 of thetilt cylinder 22 is inserted in a through-hole 23 d (refer to FIG. 6)penetrating through the seat portion 23 a in the up-down direction. Thelower end portion of the cylinder main body 26 of the tilt cylinder 22is disposed between the pair of projections 23 b. The lower end portionof the cylinder main body 26 of the tilt cylinder 22 is joined to thepair of projections 23 b via the lower pin 28. The pump 30, the tank 31,and the electric motor 32 are supported by the support portion 23 c.

The pump 30, the tank 31, and the electric motor 32 are disposedrearward relative to the tilt cylinder 22. The lateral side of the pump30, the tank 31, and the electric motor 32 is opened (for example, referto FIG. 1). Therefore, the pump 30, the tank 31, and the electric motor32 are exposed. The pipes 33 project downward from the frame 23. Thepipes 33 are exposed from the frame 23. The cylinder main bodies 24 and26 are connected to the pump 30 and the tank 31 via the plurality ofpipes 33. The pipes 33 lead the hydraulic oil to the cylinders 21 and 22and the tank 31. When the pump 30 is driven by the electric motor 32,the hydraulic oil is supplied to the cylinders 21 and 22 from the pump30. When the hydraulic oil is supplied to the cylinder main bodies 24 ofthe trim cylinders 21 from the pump 30, the projecting amounts of thetrim rods 25 change. Similarly, when the hydraulic oil is supplied fromthe pump 30 to the cylinder main body 26 of the tilt cylinder 22, theprojecting amount of the tilt rod 27 changes. The cylinder main body 26of the tilt cylinder 22 has an upper oil chamber and a lower oil chamberpartitioned by a piston although they are not shown. When a load in adirection in which the projecting amount of the tilt rod 27 decreases ofthe loads to be applied to the tilt cylinder 22 increases, the pressureof the lower oil chamber increases. When the pressure of the lower oilchamber reaches a predetermined value, the relief valve (not shown)opens and the hydraulic oil is accordingly discharged from the lower oilchamber. Accordingly, the pressure of the lower oil chamber decreases,and the projecting amount of the tilt rod 27 decreases.

FIG. 6 is a partial sectional view of a portion of the first marinevessel propulsion apparatus 1 including the tilt mechanism 19 accordingto the first preferred embodiment of the present invention. FIG. 7 andFIG. 8 are side views of a portion of the first marine vessel propulsionapparatus 1 including the tilt mechanism 19 according to the firstpreferred embodiment of the present invention. FIG. 7 shows a positionof the tilt bracket 13 when the outboard motor 2 is in a referenceposture, and FIG. 8 shows a position of the tilt bracket 13 when theoutboard motor 2 is fully tilted up (when the tilting angle of theoutboard motor 2 is a full tilt-up angle).

As shown in FIG. 6, the intermediate portion 18 of the steering shaft 11is tubular. The joint portion 17 of the steering shaft 11 has athrough-hole 34 penetrating through the joint portion 17 in the up-downdirection. The inside of the tubular portion 16 of the steering shaft 11is connected to the through-hole 34 of the joint portion 17 via theinside of the intermediate portion 18. The tilt cylinder 22 is insertedin the steering shaft 11. The cylinder main body 26 is disposed insidethe tubular portion 16. The lower end portion of the tubular portion 16is joined to the frame 23. The frame 23 turns around the steering axisL3 together with the steering shaft 11. As described above, thecylinders 21 and 22, the pump 30, the tank 31, the electric motor 32,and the pipes 33 are held by the frame 23. Therefore, the cylinders 21and 22, the pump 30, the tank 31, the electric motor 32, and the pipes33 turn around the steering axis L3 together with the steering shaft 11.

The upper end portion of the tilt rod 27 projects upward from thethrough-hole 34 of the joint portion 17. The upper end portion of thetilt rod 27 is joined to the tilt bracket 13 via an upper pin 35extending in the right-left direction. Therefore, the outboard motor 2is supported by the tilt cylinder 22. The tilt rod 27 is turnable aroundthe upper pin 35 with respect to the tilt bracket 13. The upper pin 35is an example of a first turning shaft according to the first preferredembodiment of the present invention. On the other hand, as shown in FIG.7, in a state in which the outboard motor 2 is positioned in the trimrange, the tip ends of the trim rods 25 are in contact with contactportions 36 provided on the tilt bracket 13. Therefore, in the state inwhich the outboard motor 2 is positioned in the trim range, the outboardmotor 2 is supported by the tilt cylinder 22 and the two trim cylinders21. The contact portions 36 project laterally.

When the projecting amount of the tilt rod 27 increases, the tiltbracket 13 is pushed up by the tilt rod 27 and the outboard motor 2turns up around the tilt axis L4. When the projecting amounts of thetrim rods 25 increase in the state in which the outboard motor 2 ispositioned in the trim range, the tilt bracket 13 is pushed up by thetrim rods 25 and the outboard motor 2 turns up around the tilt axis L4.The tilt cylinder 22 can hold the outboard motor 2 at an arbitraryposition between a full trim-in angle (see the outboard motor 2 shown bythe alternate long and short dashed lines in FIG. 2) and a full tilt-upangle (see the outboard motor 2 shown by the solid line in FIG. 2). Onthe other hand, the trim cylinders 21 can hold the outboard motor 2 atan arbitrary position between the full trim-in angle and a full trim-outangle (see the outboard motor 2 shown by the alternate long and twoshort dashed lines in FIG. 2). Specifically, as shown in FIG. 8, whenthe tilting angle of the outboard motor 2 becomes larger than the fulltrim-out angle, the tip ends of the trim rods 25 separate from thecontact portions 36 of the tilt bracket 13. Therefore, in the tiltrange, the outboard motor 2 is supported by the tilt cylinder 22.Further, when the outboard motor 2 moves from the trim range to the tiltrange, the amount of hydraulic oil that had been supplied to the trimcylinder 21 of the hydraulic oil fed from the pump 30 (refer to FIG. 5)is supplied to the tilt cylinder 22, and the supply flow rate of thehydraulic oil to the tilt cylinder 22 increases.

FIG. 9 is a partial sectional view of a portion of the first marinevessel propulsion apparatus 1 including a steering mechanism 20according to the first preferred embodiment of the present invention.FIG. 10 and FIG. 11 are schematic plan views of a portion of the firstmarine vessel propulsion apparatus 1 including the steering mechanism 20according to the first preferred embodiment of the present invention.

The steering mechanism 20 includes an electric motor 37, a powerconversion mechanism 38, a reduction gear mechanism 39, and a steeringcase 40. The reduction gear mechanism 39 decelerates the rotation of theelectric motor 37 and transmits the decelerated rotation to the powerconversion mechanism 38. The power conversion mechanism 38 converts thepower of the electric motor 37 transmitted by the reduction gearmechanism 39 into turning of the steering shaft 11 around the steeringaxis L3. The outboard motor 2 turns around the steering axis L3 withrespect to the transom bracket 10 according to turning of the steeringshaft 11 around the steering axis L3. The power conversion mechanism 38includes a first conversion mechanism 41 that converts the rotation ofthe electric motor 37 into linear motion, and a second conversionmechanism 42 that converts the linear motion into turning of thesteering shaft 11 around the steering axis L3 with respect to thetransom bracket 10.

The electric motor 37 includes a motor main body 43 and a rotary shaft44. The rotary shaft 44 is rotatable in the forward direction and thereverse direction opposite to the forward direction. The rotation of therotary shaft 44 is transmitted to the first conversion mechanism 41 ofthe power conversion mechanism 38 via the reduction gear mechanism 39.The electric motor 37 is housed in a steering case 40. The electricmotor 37 is disposed so that, for example, the rotary shaft 44 extendsin the right-left direction. The motor main body 43 is fixed to thesteering case 40. The steering case 40 is fixed to the transom bracket10. Therefore, the electric motor 37 is fixed to the transom bracket 10via the steering case 40. The electric motor 37 may be fixed to thetransom bracket 10 via an intermediate member such as the steering case40, or may be directly fixed to the transom bracket 10.

The first conversion mechanism 41 includes a first ball screw 45, and atubular first ball nut 46 attached to the first ball screw 45 via aplurality of balls. The second conversion mechanism 42 includes a firstrack 47 joined to the first ball nut 46, and a first pinion 48 engagedwith the first rack 47. The first ball screw 45, the first ball nut 46,and the first rack 47 are housed in the steering case 40, and are heldby the steering case 40. On the other hand, most of the first pinion 48is disposed outside the steering case 40. The first pinion 48 is joinedto the intermediate portion 18. Therefore, the first pinion 48 is joinedto the tubular portion 16 and the joint portion 17 via the intermediateportion 18. The first pinion 48 turns around the steering axis L3together with the steering shaft 11.

The first ball screw 45 extends in the right-left direction inside thesteering case 40. The rotational axis of the first ball screw 45 and therotational axis of the electric motor 37 are parallel or substantiallyparallel to each other. The first ball screw 45 is disposed rearwardrelative to the electric motor 37. Both end portions of the first ballscrew 45 are supported on the steering case 40 via bearings 49. Thefirst ball screw 45 is joined to the transom bracket 10 via the steeringcase 40, and joined to the electric motor 37 via the reduction gearmechanism 39. The rotation of the electric motor 37 is transmitted tothe first ball screw 45 via the reduction gear mechanism 39.Accordingly, the first ball screw 45 is driven to rotate by the electricmotor 37. When the first ball screw 45 rotates around the central axisof the first ball screw 45, the first ball nut 46 moves along the firstball screw 45, and the rotation of the first ball screw 45 is convertedinto linear motion of the first ball nut 46 with respect to the firstball screw 45.

The first rack 47 is provided on the outer peripheral portion of thefirst ball nut 46. The first rack 47 is, for example, integral with thefirst ball nut 46. The first rack 47 and the first ball nut 46 mayconstitute an integral member, or may constitute a member including aplurality of divided bodies joined integrally. The first rack 47includes a plurality of teeth aligned in the axial direction of thefirst ball screw 45. The first rack 47 is opposed to the steeringopening 50 provided in the steering case 40. The inside of the steeringcase 40 is connected to the inside of the housing portion 15 via atransom opening 51 provided in the housing portion 15 of the transombracket 10. When the first ball screw 45 rotates, the first rack 47moves along the first ball screw 45 together with the first ball nut 46.

The first pinion 48 projects from the outer peripheral portion of theintermediate portion 18. The first pinion 48 has, for example, a fanshape having a central axis positioned on the steering axis L3. Thefirst pinion 48 is, for example, integral with the intermediate portion18. The first pinion 48 and the intermediate portion 18 may constitutean integral member, or may constitute a member including a plurality ofdivided bodies joined integrally. The first pinion 48 enters the insideof the steering case 40 through the steering opening 50 and the transomopening 51. When the first rack 47 moves in the axial direction of thefirst ball screw 45, the position of engagement between the first rack47 and the first pinion 48 moves and the first pinion 48 turns aroundthe steering axis L3. Accordingly, the linear motion of the first ballnut 46 is converted into turning of the steering shaft 11 around thesteering axis L3.

The reduction gear mechanism 39 includes a plurality of reduction gears(a first reduction gear 52, a second reduction gear 53, a thirdreduction gear 54, and a fourth reduction gear 55). The reduction gears52 to 55 are, for example, external gears. The first reduction gear 52is joined to the rotary shaft 44 of the electric motor 37. The firstreduction gear 52 and the rotary shaft 44 are disposed coaxially witheach other. The first reduction gear 52 rotates together with the rotaryshaft 44. The first reduction gear 52 engages with the second reductiongear 53, and the second reduction gear 53 engages with the thirdreduction gear 54. The third reduction gear 54 engages with the fourthreduction gear 55. The second reduction gear 53 and the third reductiongear 54 are held rotatably by the steering case 40. The fourth reductiongear 55 is joined to the first ball screw 45. The fourth reduction gear55 and the first ball screw 45 are disposed coaxially with each other.The first ball screw 45 rotates together with the fourth reduction gear55.

The rotation of the electric motor 37 is transmitted to the first ballscrew 45 by the reduction gear mechanism 39. The power of the electricmotor 37 is amplified by deceleration of the rotation of the electricmotor 37 by the reduction gear mechanism 39. The rotation of the firstball screw 45 is converted into linear motion of the first ball nut 46with respect to the first ball screw 45 by the first ball screw 45 andthe first ball nut 46. Then, the linear motion of the first ball nut 46is converted into turning of the steering shaft 11 around the steeringaxis L3 by the first rack 47 and the first pinion 48. Accordingly, asshown in FIG. 11, the outboard motor 2 turns around the steering axis L3with respect to the transom bracket 10. When the rotary shaft 44 of theelectric motor 37 is driven to rotate in the forward direction, theoutboard motor 2 turns in one rotating direction around the steeringaxis L3, and when the rotary shaft 44 of the electric motor 37 is drivento rotate in the reverse direction, the outboard motor 2 turns in theother rotating direction around the steering axis L3.

As described above, the electric motor 37 is fixed to the transombracket 10 via the steering case 40. Therefore, when the outboard motor2 turns around the steering axis L3 with respect to the transom bracket10, the electric motor 37 does not turn around the steering axis L3 withrespect to the transom bracket 10 together with the outboard motor 2(refer to FIG. 11). Specifically, when the outboard motor 2 turns aroundthe steering axis L3 with respect to the transom bracket 10, theposition of the electric motor 37 with respect to the outboard motor 2changes. On the other hand, the electric motor 37 is fixed to thetransom bracket 10, so that when the outboard motor 2 turns around thetilt axis L4 with respect to the transom bracket 10, the electric motor37 does not turn around the tilt axis L4 with respect to the transombracket 10 together with the outboard motor 2 (refer to FIG. 2).Specifically, when the outboard motor 2 turns around the tilt axis L4with respect to the transom bracket 10, the position of the electricmotor 37 with respect to the outboard motor 2 changes.

As described above, in the first preferred embodiment, the tiltmechanism 19 that turns the outboard motor 2 around the tilt axis L4preferably includes two trim cylinders 21 and a tilt cylinder 22. Thetrim cylinders 21 turn the outboard motor 2 around the tilt axis L4between a full trim-in angle and a full trim-out angle larger than thefull trim-in angle, and support the outboard motor 2 between the fulltrim-in angle and the full trim-out angle. The tilt cylinder 22 turnsthe outboard motor 2 around the tilt axis L4 between the full trim-inangle and a full tilt-up angle larger than the full trim-out angle, andsupports the outboard motor 2 between the full trim-in angle and thefull tilt-up angle.

Thus, the tilt mechanism 19 includes two trim cylinders 21 that turn theoutboard motor 2 around the tilt axis L4 in the trim range. A range (atrim range) in which the trim cylinders 21 support the outboard motor 2is smaller than a range (a trim range and a tilt range) in which thetilt cylinder 22 supports the outboard motor 2. Specifically, in thetrim range, the outboard motor 2 is supported by the trim cylinder 21and the tilt cylinder 22, and in the tilt range, the outboard motor 2 issupported only by the tilt cylinder 22. Therefore, when the outboardmotor 2 moves from the trim range to the tilt range in a state in whichthe forward propulsive force is great, the internal pressure of the tiltcylinder 22 increases. Therefore, by discharging the hydraulic oil fromthe tilt cylinder 22 by using a relief valve, the outboard motor 2 canbe returned to the tilt range. Accordingly, when the tilting angle ofthe outboard motor 2 is adjusted in the trim range while propelling themarine vessel forward in a state in which the forward propulsive forceis great, the propeller 9 can be prevented from coming out of the waterand reducing the propulsive force to be transmitted to the hull H1.

When the outboard motor 2 moves from the trim range to the tilt range,the amount of hydraulic oil that had been supplied to the trim cylinder21 of the hydraulic oil fed from the pump 30 is supplied to the tiltcylinder 22, so that the supply flow rate of the hydraulic oil to thetilt cylinder 22 increases. Therefore, the movement speed of the tiltrod 27 of the tilt cylinder 22 increases, and the outboard motor 2 turnsaround the tilt axis L4 at a speed higher than the movement speed in thetrim range. Accordingly, the outboard motor 2 can be quickly tilted upin the tilt range. Further, unlike the conventional marine vesselpropulsion apparatus, the clamp brackets are not disposed on the lateralsides of the cylinders 21 and 22, so that the cylinders 21 and 22 can beincreased in size. Accordingly, when the outboard motor 2 is large insize or the outboard motor 2 has a high output, the increases ininternal pressure of the cylinders 21 and 22 can be minimized.

In the first preferred embodiment, the pump 30, the tank 31, theelectric motor 32, and the pipings 33 are exposed. Therefore, a user ofthe first marine vessel propulsion apparatus 1 can easily access thepump 30, the tank 31, the electric motor 32, and the pipings 33.Therefore, a user of the first marine vessel propulsion apparatus 1 caneasily perform maintenance operations such as replacement of thehydraulic oil and the pipings 33.

Second Marine Vessel Propulsion Apparatus

Next, a second marine vessel propulsion apparatus including an electricmotor fixed to the steering shaft will be described. In the descriptiongiven below, components equivalent to those shown in FIG. 1 to FIG. 11are provided with the same reference numerals as in FIG. 1, etc., anddescription thereof will be omitted.

Second Preferred Embodiment

FIG. 12 is a side view of a second marine vessel propulsion apparatus201 according to a second preferred embodiment of the present invention.FIG. 13A is a perspective view of a portion of the second marine vesselpropulsion apparatus 201 according to the second preferred embodiment ofthe present invention. FIG. 13B is an exploded perspective view of aportion of the second marine vessel propulsion apparatus 201 accordingto the second preferred embodiment of the present invention. FIG. 13C isan exploded view of a portion of the second marine vessel propulsionapparatus 201 according to the second preferred embodiment of thepresent invention. FIG. 14 is a partial side view of a portion of thesecond marine vessel propulsion apparatus 201 according to the secondpreferred embodiment of the present invention. FIG. 14 is a partial sideview of a portion of the second marine vessel propulsion apparatus 201according to the second preferred embodiment of the present invention.

The second marine vessel propulsion apparatus 201 includes the outboardmotor 2, the transom bracket 10, a steering shaft 211, and the tiltshaft 211. The second marine vessel propulsion apparatus 201 furtherincludes the tilt mechanism 19 and a steering mechanism 220. Thesteering shaft 211 includes the tubular portion 16 and the joint portion17. The joint portion 17 is joined to the upper end portion of thetubular portion 16. The joint portion 17 is, for example, integral withthe tubular portion 16. The tubular portion 16 and the joint portion 17may constitute an integral member, or may constitute a member includinga plurality of divided bodies joined integrally. Specifically, thesteering shaft 211 may be a member including a plurality of dividedbodies, or may be an integral member. The inside of the tubular portion16 is connected to the through-hole 34 of the joint portion 17. Thecylinder main body 26 of the tilt cylinder 22 is dispersed inside thetubular portion 16. The lower end portion of the tubular portion 16 isjoined to the frame 23. The upper end portion of the tilt rod 27projects upward from the through-hole 34 of the joint portion 17. Theupper end portion of the tilt rod 27 is joined to the tilt bracket 13via the upper pin 35.

FIG. 15 is a side view of the second marine vessel propulsion apparatus201 according to the second preferred embodiment of the presentinvention. FIG. 16 is a plan view of the second marine vessel propulsionapparatus 201 according to the second preferred embodiment of thepresent invention. FIG. 16 shows a state in which the outboard motor 2is positioned at a maximum rightward steering position by the solidline. FIG. 16 shows a state in which the outboard motor 2 is positionedat the steering origin by alternate long and short dashed lines, andshows a state in which the outboard motor 2 is positioned at a maximumleftward steering position by the alternate long and two short dashedlines.

The steering shaft 211 further includes a fixing portion 267 provided onthe joint portion 17. The steering case 40 is fixed to the fixingportion 267. Therefore, the electric motor 37 is fixed to the steeringshaft 211 via the steering case 40. The outboard motor 2 turns aroundthe tilt axis L4 with respect to the steering shaft 211. Therefore, asshown in FIG. 15, when the outboard motor 2 turns around the tilt axisL4 with respect to the transom bracket 10, the electric motor 37 doesnot turn around the tilt axis L4 with respect to the transom bracket 10.Specifically, when the outboard motor 2 turns around the tilt axis L4with respect to the transom bracket 10, the position of the electricmotor 37 with respect to the outboard motor 2 changes.

On the other hand, the electric motor 37 is fixed to the steering shaft211, so that when the steering shaft 211 turns around the steering axisL3, the electric motor 37 turns around the steering axis L3 togetherwith the steering shaft 211 and the outboard motor 2. Therefore, asshown in FIG. 16, when the outboard motor 2 turns around the steeringaxis L3 with respect to the transom bracket 10, the electric motor 37turns around the steering axis L3 with respect to the transom bracket 10together with the outboard motor 2. Specifically, even when the outboardmotor 2 turns around the steering axis L3 with respect to the transombracket 10, the position of the electric motor 37 with respect to theoutboard motor 2 does not change.

FIG. 17 is an exploded view of a portion of the second marine vesselpropulsion apparatus 20 according to the second preferred embodiment ofthe present invention. FIG. 18 is a partial sectional view of a portionof the second marine vessel propulsion apparatus 201 including asteering mechanism 220 according to the second preferred embodiment ofthe present invention. FIG. 19 and FIG. 20 are schematic plan views of aportion of the second marine vessel propulsion apparatus 201 includingthe steering mechanism 220 according to the second preferred embodimentof the present invention.

The steering mechanism 220 includes the electric motor 37, a powerconversion mechanism 238, the reduction gear mechanism 39, and thesteering case 40. As shown in FIG. 17, the steering mechanism 220further includes a gear case 268 and a stay 269. The power conversionmechanism 238 includes a first conversion mechanism 241 and a secondconversion mechanism 242. As shown in FIG. 18, the steering case 40 isfixed to a fixing portion 267 of the steering shaft 211, and the gearcase 268 is fixed to the steering case 40. Therefore, the gear case 268is fixed to the steering shaft 211 via the steering case 40. Thesteering shaft 211 is turnable around the steering axis L3 with respectto the transom bracket 10. Therefore, the gear case 268 is turnablearound the steering axis L3 with respect to the transom bracket 10. Asshown in FIG. 18, the gear case 268 has a gear opening 270 opposed tothe steering opening 50. The inside of the steering case 40 is connectedto the inside of the gear case 268 via the gear opening 270.

As shown in FIG. 19, the first conversion mechanism 241 includes asecond ball screw 245, and a tubular second ball nut 246 attached to thesecond ball screw 245 via a plurality of balls. The second conversionmechanism 242 includes a second rack 247 joined to the second ball nut246, and a second pinion 248 engaged with the second rack 247. Thesecond ball screw 245, the second ball nut 246, and the second rack 247are housed in the steering case 40, and held by the steering case 40. Onthe other hand, most of the second pinion 248 is housed in the gear case268. The second pinion 248 is joined to the transom bracket 10. Thesteering shaft 211 is turnable around the steering axis L3 with respectto the transom bracket 10, so that the steering shaft 211 is turnablearound the steering axis L3 with respect to the second pinion 248.

As shown in FIG. 19, the second ball screw 245 extends in the right-leftdirection inside the steering case 40. The rotational axis of the secondball screw 245 and the rotational axis of the electric motor 37 areparallel or substantially parallel to each other. The second ball screw245 is disposed rearward relative to the electric motor 37. Both endportions of the second ball screw 245 are supported on the steering case40 via bearings 49. The second ball screw 245 is joined to the transombracket 10 via the steering case 40, and joined to the electric motor 37via the reduction gear mechanism 39. The rotation of the electric motor37 is transmitted to the second ball screw 245 via the reduction gearmechanism 39. Accordingly, the second ball screw 245 is driven to rotateby the electric motor 37. When the second ball screw 245 rotates aroundthe central axis of the second ball screw 245, the second ball nut 246moves along the second ball screw 245, and the rotation of the secondball screw 245 is converted into linear motion of the second ball nut246, with respect to the second ball screw 245.

As shown in FIG. 19, the second rack 247 is provided on the outerperipheral portion of the second ball nut 246. The second rack 247 is,for example, integral with the second ball nut 246. The second rack 247and the second ball nut 246 may constitute an integral member, or mayconstitute a member including a plurality of divided bodies joinedintegrally. The second rack 247 includes a plurality of teeth aligned inthe axial direction of the second ball screw 245. The second rack 247 isopposed to the steering opening 50 provided in the steering case 40.When the second ball screw 245 rotates, the second rack 247 moves alongthe second ball screw 245 together with the second ball nut 246.

As shown in FIG. 19, the second pinion 248 includes a cylindricalportion 271 and a gear portion 272. As shown in FIG. 18, the cylindricalportion 271 of the second pinion 248 is fixed to the stay 269. The stay269 is fixed to the transom bracket 10. Therefore, the second pinion 248is fixed to the transom bracket 10 via the stay 269. The stay 269 istubular. The stay 269 and the cylindrical portion 271 are disposedcoaxially with each other. The inside of the stay 269 is connected tothe inside of the cylindrical portion 271. As shown in FIG. 18, thehousing portion 15 of the transom bracket 10 is inserted into thecylindrical portion 271 and the stay 269. The housing portion 15penetrates through the cylindrical portion 271 and the stay 269 in theup-down direction. Therefore, the cylindrical portion 271 and the stay269 surround the housing portion 15 around the steering axis L3.

As shown in FIG. 18 and FIG. 19, the second pinion 248 is covered by thegear case 268. The gear case 268 is disposed around the second pinion248. The gear portion 272 of the second pinion 248 projects from theouter peripheral portion of the cylindrical portion 271. The gearportion 272 has, for example, a fan shape having a central axispositioned on the steering axis L3. The gear portion 272 enters theinside of the steering case 40 through the steering opening 50 and thegear opening 270. The gear portion 272 engages with the second rack 247inside the steering case 40. The rotation of the electric motor 37 isconverted into turning of the steering shaft 211 around the steeringaxis L3 by the second ball screw 245, the second ball nut 246, thesecond rack 247, and the second pinion 248.

In detail, the rotation of the electric motor 37 is transmitted to thesecond ball screw 245 by the reduction gear mechanism 39. When thesecond ball screw 245 rotates, a force of relative movement in the axialdirection of the second ball screw 245 is applied to the second ballscrew 245 and the second ball nut 246. According to movement of theposition of engagement between the second rack 247 and the second pinion248, the force is converted into a force that turns the second ballscrew 245 and the second ball nut 246 around the steering axis L3.Accordingly, as shown in FIG. 20, the second ball screw 245 and thesecond ball nut 246 turn around the steering axis L3 while the secondball screw 245 moves in the axial direction of the second ball screw 245with respect to the second ball nut 246.

The second ball screw 245 is joined to the steering shaft 211 via thesteering case 40. Therefore, the second ball screw 245 turns around thesteering axis L3, and accordingly, the steering shaft 211 turns aroundthe steering axis L3 with respect to the transom bracket 10.Specifically, the rotation of the electric motor 37 is converted intolinear motion of the second ball nut 246 with respect to the second ballscrew 245 by the second ball screw 245 and the second ball nut 246.Concurrently, the linear motion of the second ball nut 246 is convertedinto turning of the steering shaft 211 around the steering axis L3 bythe second rack 247 and the second pinion 248. Accordingly, as shown inFIG. 20, the outboard motor 2 turns around the steering axis L3 withrespect to the transom bracket 10.

Third Preferred Embodiment

FIG. 21 is a back view of a portion of a second marine vessel propulsionapparatus 301 according to a third preferred embodiment of the presentinvention. FIG. 22 is a plan view of a portion of the second marinevessel propulsion apparatus 301 according to the third preferredembodiment of the present invention. FIG. 23 is a side view of a portionof the second marine vessel propulsion apparatus 301 according to thethird preferred embodiment of the present invention. In these FIG. 21 toFIG. 23, the constituent portions equivalent to the portions shown inFIG. 1 to FIG. 20 are provided with the same reference numerals as inFIG. 1, etc., and descriptions thereof will be omitted.

A main difference between the third preferred embodiment and the secondpreferred embodiment described above is that the second marine vesselpropulsion apparatus 301 preferably includes two protective covers 356that protect the tilt mechanism 19.

In detail, the two protective covers 356 are disposed at an interval inthe right-left direction. Each protective cover 356 includes an upperwall portion 357 disposed above the tank 31 or above the electric motor32, and a side wall portion 358 disposed on the lateral side of the pump30, the electric motor 32, and the trim cylinder 21 or the lateral sideof the tank 31 and the trim cylinder 21. The pump 30, the tank 31, theelectric motor 32, and the trim cylinders 21 are disposed between thetwo side wall portions 358. One protective cover 356 (left protectivecover 356) covers the pump 30, the electric motor 32, and the trimcylinder 21, and the other protective cover 356 (right protective cover356) covers the tank 31 and the trim cylinder 21. The pump 30, the tank31, the electric motor 32, and the trim cylinders 21 are protected bythe two protective covers 356. Accordingly, the pump 30, etc., areprevented from being damaged.

Each protective cover 356 is attached to, for example, the tilt bracket13. Without limiting to the tilt bracket 13, each protective cover 356may be attached to any of the transom bracket 10, the steering shaft611, the tilt shaft 12, the pump 30, the electric motor 32, and theframe 23, or may be attached to a plurality of members including any ofthe above-described members. Each protective cover 356 is attached tothe tilt bracket 13 by, for example, a plurality of bolts 359. Eachprotective cover 356 is detachable from the tilt bracket 13. When eachprotective cover 356 is detached, the pump 30, the tank 31, the electricmotor 32, and each trim cylinder 21 are exposed. Therefore, a user ofthe second marine vessel propulsion apparatus 130 can easily access thepump 30, the tank 31, the electric motor 32, and each trim cylinder 21by detaching each protective cover 356. Therefore, a user of the secondmarine vessel propulsion apparatus 130 can easily perform maintenanceoperations such as replacement of hydraulic oil.

Other Preferred Embodiments

Although preferred embodiments of the present invention are describedabove, the present invention is not limited to the contents of theabove-described first to third preferred embodiments, and can bevariously changed within the scope described in the claims.

For example, the first to third preferred embodiments describe a casewhere the steering mechanism preferably is an electric steeringmechanism including an electric motor. However, the steering mechanismis not limited to an electric steering mechanism but may be a hydraulicsteering mechanism including a hydraulic pump.

The first to third embodiments described above describe a case where aportion of the tilt cylinder (cylinder main body) is preferably housedinside the tubular portion of the steering shaft. However, the entiretilt cylinder may be housed inside the tubular portion of the steeringshaft.

The third preferred embodiment described above describes a case wherethe second marine vessel propulsion apparatus preferably includes twoprotective covers that protect the tilt mechanism. However, it is alsopossible that the first marine vessel propulsion apparatus includes twoprotective covers that protect the tilt mechanism.

The first to third preferred embodiments describe a case where one tiltcylinder and two trim cylinders are preferably provided. However, it isalso possible that one tilt cylinder and one trim cylinder are provided.

A non-limiting example of the correspondence between the componentsmentioned in the “SUMMARY OF THE INVENTION” and the components of theabove-described preferred embodiments are as follows.

Hull: Hull H1 Transom: Transom T1

Transom bracket: Transom bracket 10Steering axis: Steering axis L3,Steering shaft: Steering shaft 11, 211Tilt axis: Tilt axis L4Outboard motor: Outboard motor 2Steering mechanism: Steering mechanism 20, 220First angle: Full trim-in angleSecond angle: Full trim-out angleFirst cylinder: Trim cylinder 21Third angle: Full tilt-up angleSecond cylinder: Tilt cylinder 22Marine vessel propulsion apparatus: First marine vessel propulsionapparatus 1, second marine vessel propulsion apparatus 201, 301Tubular portion: Tubular portion 16

Pump: Pump 30

Electric motor: Electric motor 32

Piping: Piping 33

Protective cover: Protective cover 356Tilt bracket: Tilt bracket 13First turning shaft: Upper pin 35Second turning shaft: Lower pin 28

The present application corresponds to Japanese Patent Application No.2010-230852 filed in the Japan Patent Office on Oct. 13, 2010, and theentire disclosure of this application is incorporated herein byreference.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A marine vessel propulsion apparatus comprising: a transom bracketattachable to a transom of a hull; a steering shaft joined to thetransom bracket, the steering shaft being turnable around a steeringaxis extending in an up-down direction; an outboard motor joined to thesteering shaft, the outboard motor being turnable around a tilt axisextending along a plane that is perpendicular or substantiallyperpendicular to the steering axis, the outboard motor being turnablearound the steering axis together with the steering shaft; a steeringmechanism joined to the transom bracket and the steering shaft, thesteering mechanism arranged to turn the steering shaft and the outboardmotor around the steering axis with respect to the transom bracket; afirst cylinder joined to the steering shaft and the outboard motor, thefirst cylinder being arranged to turn the outboard motor around the tiltaxis between a first angle and a second angle larger than the firstangle, the first cylinder being arranged to support the outboard motorbetween the first angle and the second angle; and a second cylinderjoined to the steering shaft and the outboard motor, the second cylinderbeing arranged to turn the outboard motor around the tilt axis betweenthe first angle and a third angle larger than the second angle, thesecond cylinder being arranged to support the outboard motor between thefirst angle and the third angle.
 2. The marine vessel propulsionapparatus according to claim 1, wherein the steering shaft includes atubular portion extending along the steering axis, and at least aportion of the second cylinder is housed inside the tubular portion. 3.The marine vessel propulsion apparatus according to claim 1, wherein thefirst cylinder and the second cylinder are arranged to turn around thesteering axis together with the steering shaft.
 4. The marine vesselpropulsion apparatus according to claim 1, further comprising: a pumparranged to supply hydraulic oil to the first cylinder and the secondcylinder; an electric motor arranged to drive the pump; and a piping inwhich hydraulic oil circulates; wherein the first cylinder, the secondcylinder, the pump, the electric motor, and the piping are arranged toturn around the steering axis together with the steering shaft.
 5. Themarine vessel propulsion apparatus according to claim 4, wherein atleast a portion of the pump is exposed, and at least a portion of theelectric motor is exposed.
 6. The marine vessel propulsion apparatusaccording to claim 4, further comprising a detachable protective covercovering at least one of the pump and the electric motor.
 7. The marinevessel propulsion apparatus according to claim 4, wherein at least aportion of the piping is exposed.
 8. The marine vessel propulsionapparatus according to claim 1, wherein the outboard motor includes atilt bracket joined to the steering shaft, the tilt bracket beingturnable around the tilt axis with respect to the steering shaft.
 9. Themarine vessel propulsion apparatus according to claim 1, wherein thesecond cylinder is joined to the outboard motor via a turning shaft, thesecond cylinder being turnable around the turning shaft with respect tothe outboard motor.
 10. The marine vessel propulsion apparatus accordingto claim 1, wherein the second cylinder is joined to the first cylindervia a turning shaft, the second cylinder being turnable around theturning shaft with respect to the first cylinder.
 11. The marine vesselpropulsion apparatus according to claim 1, wherein the first cylinderand the second cylinder are disposed so as not to overlap each other asviewed in a direction orthogonal or substantially orthogonal to the tiltaxis.
 12. The marine vessel propulsion apparatus according to claim 1,wherein the marine vessel propulsion apparatus includes a pair of thefirst cylinders disposed at an interval in a direction parallel orsubstantially parallel to the tilt axis, and the second cylinder isdisposed such that the second cylinder is positioned between the pair offirst cylinders as viewed in a direction orthogonal or substantiallyorthogonal to the tilt axis.